Furnace apparatus



I m I IUUi II at Q? July'30, 1940. J. MIRRA r FURNACE APPARATUS Filed Feb. 18, 1939 2 Sheets-Sheet l INVENTOR Jamesfi zrra m ATTORNEY July 30, 1940.

J. MIRRA FURNACE APPARATUS Filed Feb. 18, 1939 2 Sheets-Sheet 2 INVENTOR lama; M z'rra ATTORNEY vuul um IIUUHI Patented July 30, 1940 UNITED STATES PATENT OFFICE 8 Claims.

This invention relates to furnace apparatus, and particularly to devices for automatically regulating the draft of a steam furnace, the present invention being an improvement over that disclosed in my patent application filed March 9, 1938, Serial No. 194,755.

It is within the contemplation of this invention to attain the various objectives of my aforesaid prior invention, but in a simpler, less cumbersome and more efiicient manner. Specifically, it is one of my objects to enable forced or induced draft apparatus to be automatically set into operation within predetermined pressure limits in a furnace provided with conventional natural draft regulating means operable within other limits, all through the medium of a single control lever.

Another one of the objects of my invention is to permit an electrically operated blower to automatically replace the natural draft of a furnace without interrupting its operation. And in this aspect of my invention, it is a further object to allow the said blower to force more than the theoretically correct amount of air required for combustion, if conditions require it, without causing undesirable back pressures and the consequent leakage of air through the furnace doors or other crevices.

It is also within the contemplation of my invention to provide means for permitting the introduction of secondary air into the furnace for burning the comparatively large quantities of combustible gases generated after the firing of fresh coal, and also for causing the automatic discontinuance of the introduction of such secondary air at certain predetermined times.

Another object of this invention is to provide a balanced draft by means of suitable regulating devices actuated by the steam pressure within the furnace, and also to effect economy in fuel consumption.

And it is still another object of my invention to enable the foregoing objectives to be attained by a simple, inexpensive and readily adjustable device.

Other objects, features and advantages will appear from the drawings and the description hereinafter given.

Referring to the drawings.

Figure 1 is a side elevation of a furnace provided with the apparatus of my invention, the parts being shown in their normal inoperative positions, and by dot-dash lines in certain operative positions.

Figure 2 is a fragmentary perspective of the secondary air arrangement, the door being shown in a position manually set by the operator after firing, for the admission of secondary air.

Figure 3 is a view similar to Figure 2, showing the door in a further elevated position under the influence of the control lever comprising a part 6 of this invention.

Figure 4 is a perspective view of the furnace equipped with the apparatus constituting my invention as disclosed in Figures 1 to 3 inclusive, certain of the parts being shown in fragmentary 10 perspective for clarity, and

Figure 5 is a fragmentary view of the valve duct associated with the blower.

In the drawings, the furnace I0 is provided with a conventional steam pressure gauge ll, 15 natural draft regulator l2, and forced draft regulator I 3. The regulator I2 is mechanical in action and contains a conventional steam-actuated diaphragm having associated therewith a plunger It in operative engagement with the 20 lever [5, the said lever being pivotally supported at the fulcrum l6, and having mounted thereon the movable weight IT, The said regulator I3 is also steam actuated and is in effect a switch of the make-and-break type, the drawings showing 35 a conventional rocker mercury tube I511 of the type referred to in my said previous application, although other forms of conventional make-andbreak switches adapted to be actuated by steam pressure may also be employed within the scope 30 of this invention. The furnace also contains a conventional swingably mounted draft door l8,

a conventional pivotally mounted check door l9 atthe rear of the furnace, a fire door 20 mounted at the hinge connections 2| and containing a 35 secondary air door 22 swingably mounted at the hinges 23.

Preferably exteriorly disposed with respect to the furnace is the blower 24, the outlet portion 25 thereof communicating with the valve duct 40 26 which is suitably connected to the pipe 21 leading preferably to the front of the furnace underneath the grate thereof. Swingably mounted upon the pivotal support 28 is the valve member 29 which, in its closed or inoperative position, obstructs the outlet 25, and in its lower or operative position opens said outlet, as indicated by the dot-dash lines of Figure 5, for communication with the pipe 21. Suitably connected to the valve 29, preferably at the said 60 pivotal mounting thereof, is the arm 30, shown positioned outside of the duct 26.

Pivotally mounted at 3| of the supporting bracket 32 positioned upon the top of the furnace, is the main control lever 33 extending, in

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the form of my invention illustrated, longitudinally of the furnace, the forward end of this lever protruding beyond and being in overhanging relation with respect to the front edge of the furnace, and the rear portion of the said lever extending sufficiently to the rear as to enable it to be operatively associated with certain of the parts in a manner to be hereinafter set forth. Slidably mounted upon the control lever 33 is the weight 34 normally tending to keep the rear arm of the lever in depressed condition and in engagement with the supporting rest 35.

The rear portion of control lever 33 has attached to it a chain 36 connected to the arm 31 associated with the excess-air valve 38 which is pivotally mounted within duct 39 communicating with the outlet conduit 40 connected to the stack 4|. The said rear portion of lever 33 has also attached thereto the cable 42 operatively mount ed over a suitably supported pulley 43, the opposite end of said chain being attached to the arm 30 of the valve member 29. The rear arm of the lever 33 has also attached thereto, preferably at a point intermediate the weight 34 and rear terminal of the lever, the chain 44 connected to the check door 19. Attached preferably although not necessarily at the region 45 where chain 44 is connected, is the cable 46 operatively mounted over the pulleys 41 and 48 and extending and being connected to the terminal 49 on the unweighted arm of lever l5. The forward arm of lever 33 has attached thereto the cable 50 the lower extremity of which is attached to the bar 5| fixedly secured to the primary draft door 18. The forward portion of control lever 33 has also operatively attached thereto the links 52, these being connected, by cable 53 mounted over pulley 54, to the relatively rigid rod 55 depending downwardly and held against forward movement by a suitably positioned pin stop as clearly illustrated particularly in Figure 4 of the drawings. The lower portion of said bar 55 contains an inwardly extending finger 56 for purposes which will be hereinafter set forth.

The secondary air door 22, in the preferred embodiment thereof, has operatively associated therewith the temporary support 51 adapted to coact with the rod 55, in a manner to be hereinafter described, whereby said door can be manually elevated and maintained in an open position until automatically released. In the specific form illustrated, a lateral wall 58 of the door contains a pin 59 upon which is pivotally mounted the temporary suport 51 illustrated as consisting of an angle bar provided with two spaced pins Gil-these pins being attached to arm 6| of the angle bar and extending transversely with respect to the pin 59 constituting the axis of rotation of temporary support 51. Attached to the door 22 is the retaining member or extension bar 62 preferably substantially parallel to the said pin 59 and adapted to extend thereover.

Normally, before the furnace is set into operation, the parts are as indicated in their full line positions of Figures 1 and 4. Due to the weight of member 34, the rear arm of the lever 33 is weighted down, the lengths of the various cables and chains being such as to keep the excess-air valve 38, and the check door I9 in a lowered and closed position, and the valve member 29 in duct 26 in its upper closed position. When the forward arm of the control lever 33, under aforesaid conditions, is raised, as illustrated, the draft door 13, due to the length of chain 50, is in a raised or open position; and the rod 55 is vertically suspended as clearly indicated. Note should also be taken that under these conditions the weighted arm of lever I5 is down, the rear end 49 of the lever being in its raised position.

When the furnace is started, a suitable switch sets the blower 24 into operation, this being electrically connected through the medium of the conductors 63 to the regulator l3. The normal position of the weight 34 is such as to merely hold the valve member 29 in its closed position by a relatively light efiort-so that when the blower is set into operation as aforesaid, the current of air directed through duct 25 will open said valve member against the action of weight 34. The air generated by the blower will pass through pipe 21 and into the furnace for providing the forced draft necessary under the circumstances. As the valve member 29 is thus moved downwardly, the arm 30 thereof will carry the cable 42 with it, thereby consequently raising the rear arm of control lever 33. When this occurs, the check door I 9 is opened, as well as the excess-air valve 38, under the influence of the chains 44 and 35 respectively. Under these conditions, the forward portion of the lever 33 is obviously lowered, thereby causing a closing of the draft door I8 and a consequent raising of the rod 55 for the admission of relatively large quantities of excess air, as will hereinafter appear. It should also be observed that when the rear arm of lever 33 is raised, there is a slack in cable 46 connected to lever l5.

Preferably at the beginning of the operation of the furnace, the secondary air door 22 should be opened because of the considerable quantities of gases generated from the fresh coal. Hence the door 22 is manually elevated and the temporary support or angle bar 51 is swung upwardly upon its mounting to the position indicated in Figure 2 where the pins are in underlying and supporting engagement with the arm 62, In this position the arm 6| of the angle bar 51 is positioned forwardly of its mounting, so that it would normally tend to swing downwardly under its own weight; but such downward swinging is obviously prevented due to the engagement of said pins 60 with arm 62. Due to the weight of support 51, the door 22 is maintained in a partially elevated position as shown in Figure 2, for the admission of secondary air therethrough, the door being so held until further elevated or released, under conditions that will hereinafter be described. It is of course necessary that the design and operation of the blower, the excess air valve 38, secondary air door 22 and check valve 19 bear a proper relation to the stack and to each other as well, so as to enable the desired operating conditions within the furnace to be properly maintained and to thereby insure a proper directional flow of air and gases.

It will be noted that in Figure 2 the rod 55 is shown extending between arm 6| of the temporary support and arm 62 of the door 22, the inwardly bent finger 56 of the rod extending transversely across the arm 62. In order to bring the parts into this position, it is preferable, before setting the door 22 and temporary support 51 as above-described, that the rod 55 be swung to its lowermost dot-dash position illustrated in Figure 1 (which is obviously possible due to the elevated position of the front arm of the lever 33 before the blower is set into operation), and thereafter the temporary support 51 raised. It is obvious that the space provided by the arms 5| 1| and 62 and the pins 30 is sufficient to operatively accommodate the rod 55 extending therebetween.

When, due to the operation of the blower, the rod 55 is elevated, as aforesaid, the finger 56 thereof is brought into engagement with the arm 62 to raise the door to the position shown in Figure 3. When this occurs the weight of the temporary support 51 will cause it to swing downwardly to its inoperative position, as indicated in Figures 3 and 4. Thus provision is made for the admission of sufiicient secondary air to burn all the combustible gases.

It is known that for best operative results the capacity of the blower should be such as to be able to introduce more than the theoretically correct amount of combustion air, so as to insure complete combustion. This frequently results, as aforesaid, in a positive pressure created within the furnace, causing a tendency of air leakage through the doors or other crevices in the furnace. To prevent such leakage, I have provided the pipe 39 extending preferably from the rear of the furnace and communicating with the chimney 4| through the excess-air valve 38. Inasmuch as such valve 38 is open when the blower is in operation, any excess air within the furnace will naturally find its way out through pipe 39 and into the stack, thereby eliminating the positive pressures conducive to leakage as abovereferred to.

When, due to the rise of the pressure of the steam within the boiler, the upper limit of regu lator I3 is reached or exceeded, the circuit through conductors E3 is opened, thereby discontinuing the action of the blower 24. When this occurs, the weight 34 will again become effective and will force the rear arm of control lever 33 downwardly, thereby causing a closing of check door I9, excess-air valve 38 and valve member 29. Simultaneously therewith the for- Ward arm of lever 33 will be elevated, thereby causing the chain 50 to elevate the draft door I8, and thus placing the entire furnace under natural draft conditions.

The raising of the forward arm of lever 33 will cause a lowering of rod 55; and inasmuch as such rod is relatively stiff, such a lowering will cause the finger thereof to become detached from the arm 62, particularly as the rod 55 under these conditions will, under its own weight, swing to the full line position shown in Figures 1 and 4. When this occurs, the door 22 will close under its own weight, inasmuch as there is no further support therefor.

As the steam pressure rises, the plunger M in the natural draft regulator l2 will move upwardly against the action of weight II; and when the upper limit is reached, the terminal 49 of lever l5 will be in its lowermost position, carrying with it the cable 46. This obviously causes a pull at point 45 of the rear arm of lever 33 to operatively elevate it. When this occurs, the forward arm of control lever 33 is consequently lowered, causing the draft door I8 to close. The consequent raising of rod 55 will obviously have no effect on the door 22, being disconnected therefrom; but if it had again been connected thereto, in the manner aforesaid, it would of course operate to elevate the door again for the admission of more secondary air. The elevated rear arm of lever 33 causes an opening of the check door I9 which, together with the effect of closing the front doors of the furnace, will serve to check the fire and consequently reduce the pressure. Although when the rear arm of lever 33 is raised, under the last-mentioned conditions, the valve member 23 is in its lowered or opened position, there can hardly be any substantial infiltration of air through duct 26, due to the interposition of the stationary blades within the blower; and should there be some infiltration, it cannot possibly offset the fire-retarding influence of the closing of the draft door and opening of the check door.

It is thus apparent that by the use of a single control lever 33, the apparatus herewith presented is considerably simpler than that described in my aforementioned patent, and yet effects similar results. In addition, it is apparent also that further provision is herein made for permitting secondary air to burn unconsumed gases, thereby not only increasing furnace efficiency but preventing the leakage of the highly obnoxious and dangerous carbon monoxide into the furnace room. The action of the secondary air door is semi-automatic, being manually operated at the time the furnace is fired, and thereafter it closes by the action of control lever 33. And furthermore, it is to be noted that by a single control lever, not only is a proper control and balance effectuated between natural draft and mechanical draft operation, but such control is elfected over the air conduit connections as to guide any excess air into the stack, thereby reducing positive pressures in the furnace with a consequent elimination of leakage.

It is of course understood that the various embodiments above-described and shown in the drawings are illustrative of my invention and not employed by way of limitation, inasmuch as numerous changes and modifications may be made within the scope of the appended claims 1without departing from the spirit of this invenion.

What I claim is:

1. In a draft regulating apparatus for a furnace having a primary natural draft inlet and a forced draft inlet, the combination of a draft door associated with the natural draft inlet, a secondary air inlet and a door operatively associated therewith, a blower, means to drive the blower, a conduit connecting the blower to the forced draft inlet, a valve member within the conduit, a pivotally mounted weighted control lever, connecting means operatively joining one arm of the lever to said draft door and said secondary air door and the other arm of the lever to said valve member, the weight on said control lever exerting a closing effort upon said valve member and an opening effort on said draft door, the connecting means being so proportioned that when the weighted arm of the control lever is in its lowered position the draft door is in its open position, the valve member in its closed position and the secondary air valve adapted for positioning in its closed position, the blower being adapted to cause the air driven thereby to open said valve member and actuate said control lever against the action of the weight thereon to cause a consequent opening of the secondary air door and a closing of the natural draft door.

2. In a draft regulating apparatus for a furnace having a primary natural draft inlet and a forced draft inlet, the combination according to claim 1, the apparatus being further provided with a check door, connecting means operatively joining the check door to that arm of the control lever connected to the valve member, the connecting means being so proportioned that when the weighted arm of the lever is in its HUUUI lowered position the check door is in its closed position, and that when the said weighted arm is raised, under the influence of the blower the check door is in its open position.

3, In a draft regulating apparatus for a furnace having a primary natural draft inlet and a forced draft inlet, the combination of a draft door associated with the natural draft inlet, a secondary air inlet and a door operatively associated therewith, a blower, means to drive the blower, a conduit connecting the blower to the forced draft inlet, a valve member within the conduit, a pipe connecting the furnace substantially at the level of the forced draft inlet to the stack of the furnace, an excess air valve within the pipe, a pivotally mounted weighted control lever, connecting means operatively joining one arm of the lever to said draft door and said secondary air door and the other arm of the lever to said valve member and said excess air valve, the weight on said control lever exerting a closing effort upon said valve member and an opening effort on said draft door, the connecting means being so proportioned that when the weighted arm of the control lever is in its lowered position the draft door is in its open position, the valve member and the excess air valve in their respective closed positions and the secondary air door adapted for positioning in its closed position, the blower being adapted to cause the air driven thereby to open said valve member and actuate said control lever against the action of the weight thereon to cause a consequent opening of the secondary air door and the excess air valve and a closing of the natural draft door.

4. A draft regulating apparatus for a furnace having a primary natural draft inlet and a mechanical draft inlet, comprising a draft door associated with the natural draft inlet, a check door, electrically operated air-propelling means operatively connected to the furnace substantially at the level of the natural draft inlet, an excess air outlet communicating with the furnace at a region substantially at the level of the natural draft inlet, an excess air valve operatively associated with said outlet, a make-and-break switch electrically connected to said air-propelling means, switch control means operatively associated with the furnace and the switch and set to actuate the switch within a predetermined boiler pressure range whereby the said air-propelling means is operatively actuated only within said range, natural draft regulator means operatively associated with the furnace and including a weighted lever balanced to be actuated only within a range of boiler pressures above the range for said air-propelling means, and a weighted control lever operably connected to the draft door, check door, and excess air valve, said control lever normally urging the draft door into an open position and permitting the check door and excess air valve to move to their closed positions, said natural draft regulator lever being connected to said control lever and being adapted to actuate the control lever against the action of the weight thereon to exert an opening effort on the check door and excess air valve and to permit a closing of the draft door.

5. In a draft regulating apparatus for a furnace having a primary natural draft inlet and a forced draft inlet, the combination of a draft door associated with the natural draft inlet, a secondary air inlet and a door operatively associated therewith, electrically operated airpropelling means operatively connected to the furnace substantially at the level of the natural draft inlet, a make-and-break switch electrically connected to said air-propelling means, switch control means operatively associated with the furnace and the switch and set to actuate the switch within a predetermined boiler pressure range whereby the said air-propelling means is operatively actuated only within said range, natural draft regulator means operatively associated with the furnace and including a weighted lever balanced to be actuated only within a. range of boiler pressures above the range for said airpropelling means, and a weighted control lever operably connected to the draft door, and said secondary air door, said control lever normally urging the draft door into an open position and permitting a closing of the secondary air door, said natural regulator lever being connected to said control lever and being adapted to actuate the control lever against the action of the weight thereon to exert an opening effort on the secondary air door and to permit a closing of the draft door.

6. In a draft regulating apparatus for a furnace having a primary natural draft inlet and a forced draft inlet, the combination according to claim 5, the connection between the control lever and the secondary air door including a link extending from the lever to and in detachable engagement with said door, an operative upward movement of the control lever producing a slack in said link and a consequent detachment thereof from said secondary air door.

7. A draft regulating apparatus for a furnace having a primary natural draft inlet and a forced draft inlet, comprising a draft door associated with the natural draft inlet, a secondary air inlet and a door operatively associated therewith, a blower, means to drive the blower, a conduit connecting the blower to the forced draft inlet, a valve member within the conduit, a pipe connecting the furnace substantially at the level of the forced draft inlet to the stack of the furnace, an excess air valve within the pipe, a check door, a make-and-break switch electrically connected to said blower, switch control means operatively associated with the furnace and the switch and set to actuate the switch within a predetermined boiler pressure range whereby the said blower is operatively actuated only within said range, natural draft regulator means operatively associated with the furnace and including a weighted lever balanced'to be-a'ctuated only within a range of boiler pressures above the range for said air-propelling means, and a pivotally mounted weighted control lever extending longitudinally over the furnace, the weighted rear arm of the control lever being directly connected by cable means to the check door and excess air valve and by cable and pulley means to the blower valve member and the unweighted arm of the natural draft regulator lever, the unweighted front arm of the con trol lever being directly connected by cable means to the draft door and by cable and pulley means to the secondary air door, said control lever under the influence of the weight thereon normally urging the draft door into an open position, the blower valve member into its closed position and permitting the check door, secondary air door and excess air valve to move to their respective closed positions, the natural draft regulator lever being adapted to actuate the control lever against the action of the weight thereon to exert an opening effort on the check door, the excess air valve and the secondary air door, and to permit a closing of the draft door.

8. In a furnace, an air door normally closed under its own weight, a pivotally mounted temporary door support, said support being adapted to swingably drop under its own weight to an inoperative position, an extension bar attached to the door and engageable with the support to maintain it in operative door-supporting position, a control lever operatively associated with the furnace, and connecting means joined to one arm of the lever and having another portion thereof normally free but adapted for underlying engagement with said extension bar whereby, upon an 25 operative movement of the lever into a predetermined position, the connecting means will engage said bar to cause an opening of the door and a release of the support from its door-supporting position, the support containing a plurality of spaced pins engageable with the extension bar when the support is in its operative door-supporting position, the connecting means containing a link having an inwardly extending finger, the link being supportable by the said support whereby the finger thereof will be in underlying relation to the extension bar and operatively engageable therewith upon the said operative movement of the lever.

JAMES MIRRA. 

